Donald Trump's signing of an anti-abortion rule on Monday could put billions of dollars in US aid funding at risk — 14 to 16 times more money than initially thought, according to health groups.

Trump revived the Mexico City policy, a Reagan-era rule prohibiting foreign groups that take US aid money from using any of their other money on abortion-related services.

In the past, the rule was only applied to family planning funding. But Trump's executive order, which was only released as offices closed on Monday, says he wants it applied to all US global health projects — affecting potentially $9.5 billion dollars in funding, according to analysis by PAI, a reproductive health group in Washington, DC.

The Trump order applies to HIV/AIDS prevention and treatment, including the Bush-era Pepfar (President's Emergency Plan for Aids Relief) program; some gender-based violence prevention programs; maternal and child health; nutrition; infectious diseases, including malaria, tuberculosis, and neglected tropical diseases; and foreign projects of the Centers for Disease Control and the National Institutes of Health.

It's unclear if the rule will affect the Global Fund for AIDS, Malaria and Tuberculosis, which leads prevention globally on those diseases.

The World Health Organization also receives US funding that could impacted by the rule, but those funding streams are complicated, and a WHO spokesman said it was too soon to comment on whether or how it might be affected by the rule.

"It’s truly atrocious," said Brian Dixon, the executive director of the Population Connection Action Fund (PCAF). "It might be the worst policy this country has ever come up with. It’s almost designed to hurt people."

Experts say the policy increases maternal death and abortion rates globally. But it's still anyone's guess just what all that means.

"Everyone was taken flat-footed. I was calling people in the US government who knew nothing about this," said a senior global health officer at a major international organization who asked for anonymity because they were not cleared to speak to the press. "I was sharing [the order] with people in US government who hadn’t even seen it. [The administration] didn’t even release it till the end of the day.

"That to me was a deliberate strategy: They conflated a whole bunch of things, broadly expanded it’s reach, and there’s no one to offer an interpretation of what it means because they don’t have any anybody confirmed."

Trump's order directs the secretaries of state and of health and human services to pull together a plan on this; neither of his nominees for those posts is confirmed yet.

"It's also a huge power grab. It suddenly takes all these things that have traditionally been in the legislative sphere and makes it an executive action," the health officer added, explaining that global health priorities have generally been set by Congressional budget approvals.

But the broad language of Trump's version of the rule will impact many more organizations, programs, and projects — and potentially roll back progress on a host of global health issues, like HIV/AIDS.

Andrew Fullem, the director of the HIV and Infectious Diseases Center at John Snow, Inc., a major USAID contractor, said the policy might undo years' worth of work to integrate HIV prevention, reproductive health, and primary care. Once unbundled, each health area could become a greater challenge.

"It's going to be harder for women particularly to have HIV testing and quick, immediate referrals for ARVs," he said, referring to the anti-retroviral drugs that can help HIV-positive people who follow a proper treatment course live as long as HIV-negative people. "Right now, we have program in Zambia where women are referred for HIV testing and can get ARVs all in one single day. We are now potentially going to make this far more complicated for them, and there will be far more opportunities for people to drop out."

The policy could potentially impact supplies of those life-saving drugs. The rule requires that groups sign an agreement not to provide abortions or any information related to abortion, including counseling or medical referrals — even in countries where abortion is legal. Groups that don't sign the policy will lose any US federal funding they receive — or any supplies that funding procures.

"If a group in Nigeria is doing HIV prevention and treatment and decides on principle not to go along with this policy, they'll lose access to all US-donated supplies," said Wendy Turnbull, a senior advier for international advocacy at PAI, based in Washington, DC.

The broad strokes of Trump's policy also amplify the risks of the so-called chilling effect, the pressure organizations feel to avoid even legal activities if they might seem too close to something that's illegal.

That's been especially true, experts say, about post-abortion care. After George W. Bush renewed the policy in 2000, there was confusion around whether USAID grant recipients could treat hemorrhaging pregnant women, because the hemorrhage might have been caused by a self-induced abortion.

"Women were coming in bleeding and were being turned away," Radloff remembers. In 2001, the president explicitly added an exception for post-abortion care to the policy.

It's unclear whether Trump's version of the regulation will honor that exception.

There was confusion Monday over past restrictions on US funding. Trump's press secretary, Sean Spicer, said in announcing the rule's return that the administration was "end[ing] the use of taxpayer dollars to fund abortions." US aid did not fund abortions prior to Trump's announcement; that's been illegal since 1973.

Patty Skuster, a senior policy adviser at the safe abortion access organization Ipas, said the rule further entrenches an anti-abortion stance that has little public health research to support.

"With this rule, a woman going to an HIV clinic, if she has an unwanted pregnancy, she's not going to know about abortion services, even if they are legal," Skuster said. "That's counseling and referral, from an evidence-based public health perspective, should be happening — in the same facility."

Public health research suggests women who want to end their pregnancies will do so, regardless of whether abortion is legal or US aid is in place. A 2011 study also suggest the global gag rule increases the rates of unsafe abortion, which the WHO says causes 13% of maternal deaths.

Supporters meanwhile have congratulated the president for bringing aid dollars back home. Total US foreign aid is .01% of the total federal budget, and family planning assistance is .01% of that. A 2015 study found that most Americans think US aid makes up a quarter of the federal budget.

Turnbull, of PAI, said citizens of those countries prefer not to be reliant on aid. "They want governments to be more self-sufficient," Turnbull said. "But that’s not going to make up the difference here. There's nothing that will make up the difference."

Major health players say it's too soon to know how the gap left by potentially billions in US global funds can be bridged.

"We're still trying to get our heads around it," said Marjorie Newman-Wlliams, vice president and director of international operations for Marie Stopes International, a reproductive health provider with headquarters in London. "There’s a certain vindictiveness, a mean-spiritedness, in this that is hard to comprehend, frankly."

MSI provides safe abortion services, and it always refuses to abide by the so-called global gag rule. This time around, the group will lose about $30 million, or 20% of its budget, Newman-Williams said.

"Marie Stopes never, ever used US government dollars for abortion or abortion related services," Newman-Williams said, citing much older restrictions that bar the use of aid for that purpose. "This [new rule] doesn’t change that. What it does is take money away so we that we can’t do the things we did within the scope of the law, which is contraception."

MSI estimates the rule will lead to 2.2 million more abortions, 2.1 million of them unsafe.